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Test Code LAB9757 Fragile X Syndrome

Methodology

Triplet-Repeat Primed Polymerase Chain Reaction (PCR) and Capillary Electrophoresis

 Note: Methylation analysis is not performed in the BJH MDL. If desired, peripheral blood specimens from XY individuals with a premutation or full-mutation allele can be sent to a reference laboratory for reflex methylation analysis. Please call the BJH MDL at 314-454-8685 for additional information.

Performing Laboratory

Barnes-Jewish Hospital Molecular Diagnostics Laboratory (BJH MDL)

Specimen Requirements

Forms: Molecular Diagnostics Requisition

 

Submit only 1 of the following specimens:

 

Specimen Type: Whole blood

Container/Tube: Lavender top (EDTA)

Specimen Volume: Full tube

Specimen Minimum Volume: 3-5 mL

Collection Instructions: Invert several times to mix blood. Clotted blood is not acceptable.

Additional Information: Specimen cannot be frozen.

 

Specimen Type: Amniotic Fluid

Container/Tube: Specimen container

Specimen Volume: 1 x 106 nucleated cells

Collection Instructions: Send cells in cell medium.

Note: Grossly bloody amniotic fluid will be assessed for maternal cell contamination via STR identity testing. Amniotic fluid may be rejected if significant maternal cell contamination is detected. STR identity testing requires a pure maternal sample for comparison (whole blood (EDTA)) and requires a separate clinician order. Please call the BJH MDL at 314-454-8685 for additional collection and ordering instructions.

Specimen Transport Temperature

Ambient/Refrigerate/Frozen NO

Reference Values

Normal alleles: 5-44 CGG repeats

Intermediate (grey zone) alleles: 45-54 CGG repeats

Premutation alleles: 55-200 CGG repeats

Full mutation alleles: >200 CGG repeats

An interpretive report will be provided.

Literature Reference:

Warren ST, Nelson DL. Advances in molecular analysis of Fragile X syndrome. JAMA 16 February 1994;271:536-42.

Jacquemont S, Hagerman R, Leehey M, et al. Penetrance of the Fragile X-associated tremor/ataxia syndrome in a premutation carrier population. JAMA 2004;191,No. 4.J

Day(s) Test Set Up

Monday
Turnaround Time:
STAT: not available
Routine: 5 to 7 business days

Test Classification and CPT Coding

81243 

 

Additional Information

For BJH Laboratory Use Only
Analyte Stability:

Blood is stable 0 to 4 hours at ambient temperature, up to 168 hours refrigerated.

Laboratory Processing Instructions:
Test performed in BJH MDL.